Method for adjusting the amplification of a high frequency signal

ABSTRACT

The present invention relates to a method for adjusting the amplification of a high frequency signal, a transmitter or receiver unit and a communication system. The aim of the invention is to provide a method and device for improved use of a polar-loop concept in a transmitter, especially for a mobile radio link. According to the method for adjusting the amplification of a high frequency signal, wherein the phase angle and the amplitude of an error-free input signal are separated from each other with a defined part of an output signal and readjusted, an output voltage of a battery voltage modulator is evaluated as a measure for an error at the output of a transmitter amplifier and taken into account in order to provide a correction.

[0001] The present invention relates to a method for controlling the gain of a radio-frequency signal, to a transmitting and/or receiving unit and to a communications system.

[0002] Particularly in the case of mobile radio links, modulation methods which influence both the amplitude or an envelope curve and the phase angle of the signal to be transmitted are used in order to increase the transmission rate. Examples of this are the relatively modern variants of the Global Standard for Mobile Communication GSM, such as Enhanced data rate for GSM evolution or EDGE, and code-division multiplexing, or code-division multiple access CDMA.

[0003] A transmitter for a mobile radio link such as this is subject to stringent linearity requirements, in order to prevent errors during transmission. A significant proportion of the nonlinearity of a transmitter such as this is caused in the transmitter amplifier. According to the prior art, the so-called polar loop concept is used, for example, in order to linearize this transmitter amplifier. In this method, the amplitude modulation is applied to the transmission signal separately from the phase modulation, with two separate control loops being provided for this purpose. The method can be implemented in a polar loop transmitter by, for example, modulation of the supply voltage of a power amplifier which is operated highly nonlinearly in the C, D or E mode. On the basis of the polar loop concept, optimized efficiency transmitter amplifiers can be used which, in addition to compliance with a required linearity, also reduce the current that is drawn. Since, particularly in a mobile radio link, at least one subscriber terminal is in the form of a mobile telephone, this considerably reduces the costs for a rechargeable battery for a mobile telephone, and/or increases the maximum operating time of a charged battery set.

[0004] If the transmitter amplifier is mismatched as a result of impedance changes in an antenna, such as those which occur in the case of large antennas as a result, for example, of a wind load and in the case of mobile telephones as a result, for example, of a change in the distance between the head and the antenna, the control gradient of the transmitter amplifier changes. The control loop bandwidth of the amplitude control loop is thus also changed. This leads to undesirable distortion of the output voltage which is evident in particular in a deterioration in the modulation spectrum, which may be sufficiently severe to contravene the spectrum mask which is subject to a fixed specification by virtue of a Standard.

[0005] One known solution to this problem is to isolate the transmitter amplifier from the antenna by the use of circulators or isolators. However, circulators are relatively narrowband components, so that two or more circulators must be interconnected in order to cover a wider bandwidth. Furthermore, these components are very expensive and, in addition, occupy rather a large amount of space, as a result of which the actually highly advantageous polar loop concept is not financially acceptable, particularly in so-called multiband appliances, owing to the use of a number of circulators.

[0006] In the radio transmission systems which have been mentioned above by way of an example, the modulation of the transmission signal includes amplitude modulation. The modulation may be provided, for example, by variation of the drain voltage in the case of field-effect transistors, or of the collector voltage in the case of bipolar transistors and the anode voltage when electronic valves are used in the transmitter amplifier. Parasitic phase modulation occurs in this case because the phase of the complex transfer function S₂₁ is dependent on the drain/source voltage U_(DS) or U_(D) or on the collector/emitter voltage U_(CE). If the modulation that is used in the radio transmission system is a combination of amplitude modulation and phase modulation, as is the case, for example, in G2.5 and G3 mobile radio systems, then the phase modulation component is corrupted by an additional parasitic phase modulation component Δφ(A(t)). This corruption results, for example, in an increased error vector and/or an increased bandwidth requirement.

[0007] During operation of the transmitter amplifier for a mobile radio link, the respectively involved control loops may be affected both as a result of parasitic phase modulation and by impedance changes in an antenna or the like.

[0008] The present invention is therefore based on the object of proposing a method and an apparatus for improved utilization of a polar loop concept in a transmitter, in particular for a mobile radio link.

[0009] According to the invention, this object is achieved by a method having the features of claim 1 and by a transmitting and/or receiving unit having the features of claim 9 or of claim 25. Furthermore, this object is achieved by a communications system having the features of claim 6 or claim 30. The dependent claims each define preferred and advantageous embodiments of the present invention.

[0010] The fundamental idea of the present invention is to assess an output voltage from a battery voltage modulator as a measure of any error at an output of a transmitting amplifier, and to use the output voltage to produce a correction value. Particular embodiments of this method relate to the compensation for an error resulting from a change in the control loop bandwidth of the amplitude control loop (dependent claim 2) and compensation for an error resulting from parasitic phase modulation (dependent claim 17). The respective measures in order to compensate for parasitic phase modulation and for any change in the control loop bandwidth of the amplitude control loop may, of course, in each case be combined with one another. In this context, it is possible, in particular to combine functionally similar components of the transmitting and/or receiving unit as claimed in claim 4 and of the transmitting and/or receiving unit as claimed in claim 25 to form one component. This also applies to the communications systems as claimed in claims 16 or 30.

[0011] A method according to the invention as claimed in claim 2 is accordingly distinguished in that an output voltage from the battery voltage modulator is used as a measure of the variation of the control loop bandwidth of the amplitude control loop in a polar loop transmitter in the event of a mismatch at the output of the transmitter amplifier. This signal advantageously already exists in known circuits, so that no additional measurement points and/or measurement apparatuses need be provided. It is thus advantageously possible to use the output voltage from the battery voltage modulator as an indicator of a change in the control loop bandwidth of the amplitude control loop, and to use this for correction purposes.

[0012] In one significant development of the invention, a correction value is determined using an input signal and an instantaneous output voltage from the battery voltage modulator and is used to compensate for the variation in the control gradient of the transmitter amplifier, and thus for the control loop bandwidth. In one preferred embodiment of the invention, a control signal for the battery voltage modulator is varied by this correction value, in particular by driving a controlled intermediate amplifier. Furthermore, the control loop bandwidth is, in particular, indirectly readjusted by means of a new control loop on the basis of a family of characteristics which is recorded once for a transmitter amplifier or is recorded for an entire range of transmitter amplifiers.

[0013] A family of characteristics such as this is preferably also stored in a memory, taking into account tolerance values. The required correction values can be read quickly in a known manner via accesses having A/D and D/A converters.

[0014] A method according to the invention can be integrated with very little additional circuit complexity in a transmitting and/or receiving unit. The additional space required and the intrinsic power demand of an extended circuit are advantageously very small. Furthermore, the creation or recording of a family of characteristics, as mentioned above, is associated with relatively little complexity, so that a method according to the invention can be used particularly advantageously in a communications system which comprises at least one transmission path according to a mobile radio standard. In particular, a transmitting and/or receiving unit is in the form of a mobile telephone, as part of a communications system such as this. However, owing to the advantages mentioned above, a method according to the invention can also advantageously be used in or retrofitted to any other transmitting and/or receiving unit.

[0015] A method according to the invention as claimed in claim 17 is distinguished in that an output voltage from the battery voltage modulator is assessed as a measure of any phase error to be expected from the amplifier in the transmitter amplifier. The output voltage from the battery voltage modulator can be accessed easily and directly as a signal within a circuit operating on the basis of this method, so that there is no need to provide any additional measurement points and/or measurement apparatuses. This advantageously makes it possible to use the output voltage from the battery voltage modulator as an indicator of any phase error in the amplifier, and to use this for correction purposes.

[0016] In one significant development of the invention, a correction value is determined using an instantaneous output voltage from the battery voltage modulator, and this correction value is essentially used to compensate for the erroneous change in the phase transmission through the transmitter amplifier. In one preferred embodiment of the invention, this correction value is taken from a characteristic. A characteristic such as this is preferably also stored digitally in a memory, taking into account tolerance values. The required correction values can be read quickly in a known manner via accesses with A/D and D/A converters. The phase response is also readjusted by means of a compensation circuit on the basis of a family of characteristics which is recorded once for a transmitter amplifier, or is recorded for an entire range of transmitter amplifiers.

[0017] In one preferred embodiment of the invention, the phase of the complex circuit parameter S₂₁ of the transmitter amplifier is a rising function of the voltage U_(DS) or U_(CE). The parasitic phase modulation can thus be neutralized by the phase of the parameter S₂₁ being a falling function of the gate/source voltage U_(GS) or the base current I_(B). This falling function is then linked in some suitable manner to U_(DS) or U_(CE), the output signal from the battery voltage modulator. In one preferred embodiment of the invention, the parasitic influence of the supply voltage of the transmitter amplifier, which carries the signal, and the effect of any change in the operating point in time with the payload signal counteract one another. A correction value for a specific band is thus permanently set via a simple voltage divider. A corresponding circuit and measurement results will also be described on the basis of a specific exemplary embodiment and with reference to the drawings.

[0018] A method according to the invention can be integrated in a transmitting and/or receiving unit with very little additional circuit complexity. The additional space requirement and intrinsic energy demand of an extended circuit are advantageously very small. The creation or recording of the characteristics mentioned above is also associated with relatively little effort, so that a method according to the invention can be used particularly advantageously in a communications system which comprises at least one transmission path according to a mobile radio standard. In particular, a transmitting and/or receiving unit is in the form of a mobile telephone, as part of a communications system such as this. However, owing to the advantages mentioned above, a method according to the invention can also advantageously be used in or retrofitted to any other transmitting and/or receiving unit. The compact form also allows a high degree of integration for multiband systems for mobile telephones.

[0019] The present invention will be explained in the following text using preferred exemplary embodiments and with reference to the attached drawing.

[0020]FIG. 1 shows a simplified block diagram relating to the implementation of a known polar loop control with a battery voltage modulator, and

[0021]FIG. 2 shows a simplified block diagram of an embodiment according to the invention.

[0022]FIG. 3 shows a simplified block diagram relating to the implementation of amplitude modulation with a transmitter amplifier as a component of the circuit shown in FIG. 1;

[0023]FIG. 4 shows a simplified block diagram of an embodiment according to the invention with a compensation circuit;

[0024]FIG. 5 shows measurement data for a real amplifier, in the form of the gain and phase angle, for one input power level and

[0025]FIG. 6 illustrates, in the form of a graph, the data for another input power level as curves;

[0026]FIG. 7 shows a measured spectrum without, and

[0027]FIG. 8 shows a measured spectrum of the same amplifier subject to the influence of a compensation network according to the invention, and, finally,

[0028]FIG. 9 shows the configuration chosen in the present exemplary embodiment, analogously to the illustration shown in FIG. 4.

[0029] In detail, FIG. 2 relates to an exemplary embodiment of the invention in which an error at the output of a transmitter amplifier is due to a change in the control loop bandwidth of an amplitude control loop, while FIGS. 3 to 9 relate to an exemplary embodiment of the invention in which the aim is to neutralize parasitic phase modulation.

[0030] In a polar loop control system, the phase angle and amplitude of an error-free input signal U_(nom) to a polar loop transmitter PLS are compared with a defined part of an output signal U_(out), and are readjusted if necessary, in separate control loops in a phase comparator φ and an amplitude comparator A. The defined part of the output signal U_(out) is fed back to the input of the polar loop transmitter PLS, on a trial and error basis, via a feedback path F and provided with a matching or attenuation factor a. In this case, the output signal U_(out) represents the signal which is supplied to an antenna ANT from the polar loop transmitter PLS. A directional coupler RK between the output of the transmitter amplifier PA and the antenna ANT separates a forward wave of the output signal U_(out) and a backward wave, which is produced by reflection by the antenna ANT, which is generally not matched to the characteristic impedance of the supply line. The signal U_(out) thus represents only the forward wave.

[0031] The output signal from the phase comparator φ regulates the phase angle of U_(out) at the nominal value that is predetermined by U_(nom) by means of a voltage controlled oscillator VCO. By means of the control signal U_(am) and via the battery voltage modulator M, the amplitude comparator A influences the supply voltage U_(D) to a transmitter amplifier PA, and hence the envelope curve of the output voltage, such that the amplitude of U_(out) is likewise an error-free map of the amplitude of U_(nom).

[0032] However, the gradient of the transmitter amplifier PA is dependent on the respective load of a termination. A mismatch caused by a change in the impedance of the antenna ANT thus also varies the gradient of the transmitter amplifier PA. Impedance changes such as these occur quickly as a result of changes in the environment and/or in the geometry of the antenna ANT. These occur correspondingly frequently. If the output signal U_(out) is also kept essentially constant by means of the amplitude control loop, then any change in the gradient of the transmitter amplifier PA directly affects the control loop bandwidth of the amplitude control loop, however, and hence the modulation spectrum, resulting in unacceptable distortion.

[0033] The aim of an embodiment according to the invention as shown in FIG. 2 is to keep the control loop bandwidth of the amplitude control loop in the polar loop transmitter PLS constant, even in the event of a change to the impedance of the antennas ANT and in the event of a mismatch caused by this, in order in this way to ensure the necessary linearity of the output signal U_(out) while complying with a predetermined modulation spectrum, a specific bit error rate, etc. However, there is no need to use expensive and large circulators in this case.

[0034] A mismatch of the transmitter amplifier PA caused by impedance changes from an antenna ANT will produce a change in the output signal U_(out). The signal U_(c) is produced at the output of the battery voltage modulator M via the feedback path F and is readjusted via the amplitude control loop until any error between U_(out) and a predetermined value is regulated out. U_(D) can thus be used as an indicator of load changes.

[0035] In the following text, the output voltage U_(c) from the battery voltage modulator M is assessed as a measure of the variation of the control loop bandwidth of the amplitude control loop in the polar loop transmitter PLS, in response to a mismatch at the output of the transmitter amplifier PA. A correction value U_(corr) is produced on the basis of this assessment and can be used to produce the original control loop bandwidth once again. This is advantageously based on a circuit as shown in FIG. 1, which is extended only slightly by a small number of circuit additions, in a manner illustrated in the figure in FIG. 2.

[0036] For assessment and subsequent correction, the instantaneous output voltage U_(D) from the battery voltage modulator M is read by a system controller SC which has been newly added in the circuit shown in FIG. 2. Since U_(nom) and any attenuation a in the feedback path F of the system controller are known, the instantaneous control gradient S of the transmitter amplifier PA $S = {\frac{U_{out}}{U_{D}} = \frac{\left( {U_{nom} - a} \right)}{U_{D}}}$

[0037] can thus be determined.

[0038] The output voltage U_(D) from the battery voltage modulator M is converted from the battery voltage U_(DD) by means of an analog/digital converter ADC for processing. In the present embodiment of the invention, a correction value U_(corr) can be found by means of a look-up table LUT, by comparison of a digitized value with a gradient S, that is determined once, for the transmitter amplifier PA on standard termination. The correction value U_(corr) is either predetermined directly or, as described in the present exemplary embodiment, by means of a digital/analog converter DAC in a variable amplifier VGA. In this case, the correction value U_(corr) results in the control loop bandwidth of the amplitude control loop being corrected, and in the original control loop bandwidth being restored. A characteristic which remains essentially the same over the predetermined bandwidth while complying with the Standards is thus guaranteed in this case for a polar loop transmitter PLS as shown in FIG. 2.

[0039] The advantages of the described embodiment, for example in the case of a dual-band mobile radio, are, in particular, that it is possible to use static or nonvolatile memories which can be loaded as required with values for each selectable band. Operation in two or more bands is thus dependent only on a memory LUT of slightly larger size but does not result in any other change to the circuit. The advantage of compact construction is thus retained for every application of an apparatus according to the invention. In consequence, the extension to the system controller SC can itself be represented as a large-scale integrated circuit. A system controller SC can then be retrofitted in a particularly simple manner in any polar loop transmitter PLS. However, the entire circuit of the polar loop transmitter PLS may also be in the form of a large-scale integrated circuit, and there is advantageously no need for any further hybrid components such as isolators, even for mobile telephone systems covering more multiple bands. An apparatus according to the invention with a very compact form is thus suitable for use in two or more frequency bands.

[0040] The illustration in FIG. 3, which relates to the embodiment of the invention for neutralization of parasitic phase modulation, shows only one enlarged detail, which is surrounded by a dashed line in FIG. 1, of the polar loop transmitter PLS with the applied signals. A battery voltage monitor M is connected to a supply voltage U_(DD), which is fed into the transmitter amplifier PA by means of the signal U_(in) as an input signal, as the output signal U_(D)(A(t)) whose amplitude varies in accordance with the preset variable A(t). On the basis of U_(D)(A(t)) an input signal U_(in) as a cosine oscillation is amplified with a variable-time phase term φ(t) and information in the amplitude A(t). The output signal from this circuit is thus a signal which oscillates in the form of a cosine wave with time t with a variable-time amplitude A(t), a variable-time phase term φ(t) and an additional phase shift Δφ(A(t)) which is dependent on the magnitude of the input signal U_(in). This additional phase shift Δφ(A(t)) makes itself evident in a negative manner as a phase error or as parasitic phase modulation in the output signal, by means of an information error.

[0041] The aim of an embodiment according to the invention as shown in FIG. 3 is to keep any parasitic phase modulation Δφ(A(t)) with the resultant errors in a signal to be transmitted, as small as possible, in order to ensure the required linearity in the output signal U_(out) while complying with a predetermined modulation spectrum, a specific bit error rate, etc. This very considerably reduces the load on the actual phase locked loop illustrated in FIG. 1. The output voltage U_(D)(A(t)) from the battery voltage modulator M will be assessed in the following text as a measure of any parasitic phase modulation Δφ of the transmitter amplifier PA. The production of a correction value k by means of which the phase eror Δφ can be minimized, will be described on the basis of this assessment. This is advantageously based on a circuit as shown in FIG. 1, which is extended only slightly, by minor circuit additions, in a manner which is illustrated in the illustration in FIG. 4.

[0042] In the illustration shown in FIG. 4, the signal U_(D)(A(t)) is used to largely eliminate the phase error Δφ(A(t)) to be expected, by determining a correction variable k as a function of the magnitude of the signal U_(D)(A(t)) from a circuit K, and by feeding this together with the cosine oscillation U_(in) as an input signal into the transmitter amplifier PA. In the present exemplary embodiment, k is a factor by means of which the magnitude of the signal U_(D)(A(t)) is adapted in a suitable manner in order to minimize the phase error Δφ(A(t)). According to the invention, the correction is introduced via the bias voltage U_(bias), by means of the signal U_(GS) in order to change the operating point of the transmitter amplifier PA. In this context, it has been found that a change in the operating point setting in time with the signal U_(D)(A(t)) has an effect which counteracts the parasitic phase effect. An essentially undisturbed phase profile is thus guaranteed for a polar loop transmitter PLS as shown in the illustration in FIG. 4, while complying with a specified Standard.

[0043] Measurement data were recorded on a real component in order to carry out amplitude modulation in an EDGE transmitter which is operating on the polar loop principle. An MOS transistor amplifier was used for this purpose in the exemplary embodiment which is discussed in the following text. The magnitude and phase of the complex parameter S₂₁ were measured as a function of U_(DS) using values of the so-called bias voltage U_(bias) and in each case two different input power levels P_(in) as parameters. In the end, the connection of the bias voltage U_(bias) via a voltage divider controls the gates of the transistors (which are contained in the component) of the transmitter amplifier PA in order to adjust the operating point. As the illustrations in the form of graphs of the measurement values in FIGS. 5 and 6 show, the phase of the variable S₂₁ rises monotonally with the voltage U_(DS), the abscissa.

[0044] In contrast, the phase of S₂₁ falls as the voltage U_(bias) increases. The input power P_(in) in the illustration in FIG. 5 was chosen to be higher than that in FIG. 6, although this does not have an excessively significant effect on the phase profile.

[0045]FIG. 7 shows the modulation spectrum of the EDGE transmitter for a constant bias voltage U_(bias). The spectrum is asymmetric, which clearly indicates that undesirable phase modulation has occurred. Compliance with a predetermined modulation spectrum or adjacent channel power rejection ACPR for a mid-frequency from about +400 kHz is accordingly approximately 56 dBc, as measured between the positions marked by two arrows.

[0046]FIG. 8 shows the modulation spectrum for the same EDGE transmitter with the modification that the so-called bias input is connected to the drain voltage U_(D)(A(t)) via a simple resistive voltage divider in order to set the correction factor k. The spectrum when using this simple correction circuit K is largely symmetrical, as a result of which only the component of undesirable phase modulation in the output signal will have been reduced to a very major extent. Furthermore, the attenuation with an adjacent channel ACPR at −400 kHz and +400 kHz away from the mid-frequency is now uniformly an improved value of approximately 61 dBc, once again measured between the arrows at the positions shown in FIG. 4.

[0047] The illustration in FIG. 9 shows the configuration chosen in the present exemplary embodiment, which is analogous to the illustration in FIG. 4. In this embodiment, the correction circuit K for adjustment of the correction factor k has only a simple resistive voltage divider, whose free end point is at a potential V, which can be set such that it is fixed. Two or more such correction circuits K can be provided with different potentials V, which are connected as required or after selection of a band, for use in different bands.

[0048] The advantages of the described embodiment are, for example, in the case of dual-band mobile radio, in particular, that static or nonvolatile memories can be used for the correction variables k, in particular in the form of fixed voltage dividers, to which a value is applied for each of the bands which can be selected. Operation in two or more bands is thus dependent only on a circuit K which is larger to a small extent, but does not result in any other change to the circuit. The advantage of a compact construction is thus retained for every application of an apparatus according to the invention. However, the entire circuit of the polar loop transmitter PLS may also be in the form of a large-scale integrated circuit. An apparatus according to the invention and with a very compact form is thus suitable for use in two or more frequency bands, in particular for mobile telephones designed for multiband systems. 

1. A method for controlling the gain of a radio-frequency signal, in which the phase angle and amplitude of an error-free input signal (U_(nom)) are compared separately from one another with a defined part of an output signal (U_(out)) and are readjusted, characterized in that an output voltage (U_(c)) from a battery voltage modulator (M) is assessed as a measure of any error at an output of a transmitter amplifier (PA) and is used to produce a correction.
 2. The method as claimed in claim 1, characterized in that the error at the output of the transmitter amplifier (PA) is a change in the control loop bandwidth of the amplitude control loop in the event of a mismatch and/or a change in the impedance of an antenna (ANT).
 3. The method as claimed in claim 2, characterized in that a correction value (U_(corr)) in order to compensate for the control loop bandwidth change in the amplitude control loop is determined using an input signal (U_(nom)) and an instantaneous output voltage (U_(D)) from the battery voltage modulator (M).
 4. The method as claimed in one of the preceding claims, characterized in that a control signal (U_(am)) for a battery voltage modulator (M) is varied by means of a correction value (U_(corr)).
 5. The method as claimed in the preceding claim, characterized in that the control signal (U_(am)) for the amplitude modulator (M) is varied by driving a controlled intermediate amplifier (VGA).
 6. The method as claimed in one of the preceding claims, characterized in that correction values (U_(corr)) and/or a family of characteristics are/is stored in a memory (LUT), in particular taking into account tolerance values.
 7. The method as claimed in one of the preceding claims, characterized in that the correction values (U_(corr)) are read and/or generated via accesses with A/D and D/A converters (DAC, ADC).
 8. The method as claimed in the preceding claim, characterized in that correction values (U_(corr)) and/or a family of characteristics are/is stored and/or produced in a memory (LUT) to a respectively predetermined mobile radio standard in a system controller (SC).
 9. A transmitting and/or receiving unit, in particular for implementation of a method as claimed in one of the preceding claims, wherein a phase comparator (φ) and an amplitude comparator (A) are provided for separate comparison of a phase angle and of an amplitude of an error-free input signal (U_(nom)) with a defined part of an output signal (U_(out)) and, if appropriate, for any necessary readjustment, characterized in that a system controller (SC) is provided for evaluation of an instantaneous output voltage (U_(D)) from a battery voltage modulator (M) in an amplitude control loop, and the system controller (SC) is designed to emit correction values (U_(corr)) in order to compensate for any control loop bandwidth change in the amplitude control loop.
 10. The transmitting and/or receiving unit as claimed in the preceding claim, characterized in that, in the amplitude control loop, a controlled intermediate amplifier (VGA) is connected upstream of a battery voltage modulator (M), which is connected to the system controller (SC) via a control signal (U_(am)) in order to adjust correction values (U_(corr)) in order to compensate for any change in the control loop bandwidth.
 11. The transmitting and/or receiving unit as claimed in one of the two preceding claims, characterized in that the system controller (SC) comprises an apparatus in which correction values (U_(corr)) and/or a family of characteristics are/is stored, in particular in a means which is in the form of a nonvolatile memory (LUT).
 12. The transmitting and/or receiving unit as claimed in one of the preceding claims 8 to 10, characterized in that the system controller (SC) comprises an apparatus for reading and/or conversion of correction values (U_(corr)), with this apparatus in particular being in the form of an A/D and/or D/A converter (DAC, ADC).
 13. The transmitting and/or receiving unit as claimed in one of the preceding claims 8 to 11., characterized in that the system controller (SC) is in the form of a large-scale integrated assembly and/or an integrated circuit.
 14. The transmitting and/or receiving unit as claimed in one of the preceding claims 9 to 13, characterized in that the transmitting and/or receiving unit has a system controller (SC) suitable for use in two or more frequency bands.
 15. The transmitting and/or receiving unit as claimed in one of the preceding claims 9 to 14, characterized in that the transmitting and/or receiving unit is in the form of a mobile radio or a mobile telephone.
 16. A communications system for transmission of data and/or information via at least one radio interface, characterized in that the communications system comprises at least one transmitting and/or receiving unit which is designed as claimed in one of the preceding claims 9 to 15 and/or for implementation of a method as claimed in one of claims 1 to
 8. 17. The method as claimed in claim 1, characterized in that the error is a phase error (Δφ) to be expected on the basis of parasitic phase modulation.
 18. The method as claimed in claim 17, characterized in that a correction value (k), in order to compensate for parasitic phase modulation (Δφ(A(t))) is determined by means of an instantaneous output voltage (U_(D)) from the battery voltage modulator (M).
 19. The method as claimed in one of the two preceding claims, characterized in that correction values (k) and/or a family of characteristics are/is stored in a correction circuit (K), in particular taking into account tolerance values.
 20. The method as claimed in one of claims 17 to 19, characterized in that the correction values (k) are read and/or generated via accesses with A/D and D/A converters.
 21. The method as claimed in the preceding claim, characterized in that correction values (k) and/or a family of characteristics are/is stored and/or produced in a correction circuit (K) to a respectively predetermined mobile radio standard.
 22. The method as claimed in one of the two preceding claims, characterized in that a correction value (k) is set via a voltage divider.
 23. The method as claimed in one of claims 17 to 22, characterized in that a correction signal (U_(GS)) is prepared from the output voltage (U_(D)), from the battery voltage modulator (M) and from a correction value (k).
 24. The method as claimed in the preceding claim, characterized in that the correction signal (U_(GS)) is varied by adding the operating point of at least one transistor or an electronic valve in the transmitter amplifier (PA) to the bias voltage.
 25. A transmitting and/or receiving unit, in particular for implementation of a method as claimed in one of claims 17-24, characterized in that a correction circuit (K) is provided for evaluation of an instantaneous output voltage (U_(D)) from a battery voltage modulator (M) in an amplitude control loop, and is designed to emit correction values (k) and/or a correction voltage (U_(GS)) in order to vary an operating point of at least one transistor or one electronic valve in the transmitter amplifier (PA).
 26. The transmitting and/or receiving unit as claimed in the preceding claim, characterized in that the correction circuit (K) is in the form of a voltage divider.
 27. The transmitting and/or receiving unit as claimed in one of the two preceding claims, characterized in that the correction circuit (K) is suitable for use in two or more frequency bands.
 28. The transmitting and/or receiving unit as claimed in one of the preceding claims 25 to 27, characterized in that the correction circuit (K) is in the form of a large-scale integrated assembly and/or an integrated circuit, in particular with the transmitter amplifier (PA).
 29. The transmitting and/or receiving unit as claimed in one of the preceding claims 25 to 28, characterized in that the transmitting and/or receiving unit is in the form of a mobile radio or mobile telephone.
 30. A communications system for transmission of data and/or information via at least one radio interface, characterized in that the communications system comprises at least one transmitting and/or receiving unit which is designed as claimed in one of the preceding claims 25 to 29, and/or for implementation of a method as claimed in one of claims 17 to
 24. 